1//===- ObjCARC.h - ObjC ARC Optimization --------------*- C++ -*-----------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8/// \file
9/// This file defines common definitions/declarations used by the ObjC ARC
10/// Optimizer. ARC stands for Automatic Reference Counting and is a system for
11/// managing reference counts for objects in Objective C.
12///
13/// WARNING: This file knows about certain library functions. It recognizes them
14/// by name, and hardwires knowledge of their semantics.
15///
16/// WARNING: This file knows about how certain Objective-C library functions are
17/// used. Naive LLVM IR transformations which would otherwise be
18/// behavior-preserving may break these assumptions.
19///
20//===----------------------------------------------------------------------===//
21
22#ifndef LLVM_LIB_TRANSFORMS_OBJCARC_OBJCARC_H
23#define LLVM_LIB_TRANSFORMS_OBJCARC_OBJCARC_H
24
25#include "llvm/ADT/StringSwitch.h"
26#include "llvm/Analysis/AliasAnalysis.h"
27#include "llvm/Analysis/ObjCARCAnalysisUtils.h"
28#include "llvm/Analysis/ObjCARCInstKind.h"
29#include "llvm/Analysis/Passes.h"
30#include "llvm/Transforms/Utils/Local.h"
31#include "llvm/Analysis/ValueTracking.h"
32#include "llvm/IR/CallSite.h"
33#include "llvm/IR/InstIterator.h"
34#include "llvm/IR/Module.h"
35#include "llvm/Pass.h"
36#include "llvm/Transforms/ObjCARC.h"
37
38namespace llvm {
39class raw_ostream;
40}
41
42namespace llvm {
43namespace objcarc {
44
45/// Erase the given instruction.
46///
47/// Many ObjC calls return their argument verbatim,
48/// so if it's such a call and the return value has users, replace them with the
49/// argument value.
50///
51static inline void EraseInstruction(Instruction *CI) {
52  Value *OldArg = cast<CallInst>(CI)->getArgOperand(0);
53
54  bool Unused = CI->use_empty();
55
56  if (!Unused) {
57    // Replace the return value with the argument.
58    assert((IsForwarding(GetBasicARCInstKind(CI)) ||
59            (IsNoopOnNull(GetBasicARCInstKind(CI)) &&
60             IsNullOrUndef(OldArg->stripPointerCasts()))) &&
61           "Can't delete non-forwarding instruction with users!");
62    CI->replaceAllUsesWith(OldArg);
63  }
64
65  CI->eraseFromParent();
66
67  if (Unused)
68    RecursivelyDeleteTriviallyDeadInstructions(OldArg);
69}
70
71/// If Inst is a ReturnRV and its operand is a call or invoke, return the
72/// operand. Otherwise return null.
73static inline const Instruction *getreturnRVOperand(const Instruction &Inst,
74                                                    ARCInstKind Class) {
75  if (Class != ARCInstKind::RetainRV)
76    return nullptr;
77
78  const auto *Opnd = Inst.getOperand(0)->stripPointerCasts();
79  if (const auto *C = dyn_cast<CallInst>(Opnd))
80    return C;
81  return dyn_cast<InvokeInst>(Opnd);
82}
83
84/// Return the list of PHI nodes that are equivalent to PN.
85template<class PHINodeTy, class VectorTy>
86void getEquivalentPHIs(PHINodeTy &PN, VectorTy &PHIList) {
87  auto *BB = PN.getParent();
88  for (auto &P : BB->phis()) {
89    if (&P == &PN) // Do not add PN to the list.
90      continue;
91    unsigned I = 0, E = PN.getNumIncomingValues();
92    for (; I < E; ++I) {
93      auto *BB = PN.getIncomingBlock(I);
94      auto *PNOpnd = PN.getIncomingValue(I)->stripPointerCasts();
95      auto *POpnd = P.getIncomingValueForBlock(BB)->stripPointerCasts();
96      if (PNOpnd != POpnd)
97        break;
98    }
99    if (I == E)
100      PHIList.push_back(&P);
101  }
102}
103
104} // end namespace objcarc
105} // end namespace llvm
106
107#endif
108